I wouldn't go that far. I mean I love just love horror movies but man it's been years since I've actually been scared by movie. I'd say the reason it got a 50% rating is because it's a mediocre movie, simple as that. Guess with the setting and monster idea I was hoping for something along the lines of The Thing
Terrible movie. There's only so many times they can have Hartnett awkwardly decapitating vampires before it gets boring. Also, did anyone else find the incessant vampire screeching annoying as hell? The movie would have been better if there were less random acts of vampirism and more history relating why these dumb vampires were in alaska.
There's only been 12 "Horror" movies rated 80% or above on Rottentomatoes since 2000. That includes "The Excorcist" and "Donnie Darko" which were both re-releases, as well as Shaun of the Dead, which was actually a comedy. Obviously it's subjective, but to me 80% on that site is a sign of excellence...a movie most people will love. When it comes to horror movies, there just aren't many of those. Also, there are 23 "Horror" movies rated 10% or below since 2000. So it seems the genre is flooded with crap, so while 30 Days of Night may not have been a great movie in and of itself, it was enjoyable in comparison to the usual fare. But I guess that's just me.
